O’Reilly has a program that provides online access to books that have yet to be published. It’s called “Rough Cuts” and allows you to read chapters as they are written but before they are cleaned up for final publication, and it provides a discounted price for online and print editions. Given the nature of technology and the speed of change, I find early access to be quite valuable. Here are two books listed that I recommend ordering in their Rough Cuts version:
Programming Entity Framework Second Edition by Julia Lerman. This includes coverage of Entity Framework 4.0 with samples in C#.
Programming WCF Services Third Edition by Juval Lowy, which covers new features in .NET 4.0.